scholarly journals A new iron-phosphate compound (Fe7P11O38) obtained by pyrophosphate stoichiometric glass devitrification

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Pawel Goj ◽  
Aleksandra Wajda ◽  
Artur Błachowski ◽  
Pawel Stoch
Keyword(s):  
Electronic Band Structure ◽  
Magnetic Moments ◽  
Iron Phosphate ◽  
Electric Properties ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Ab Initio Simulations ◽  
Phosphate Compound ◽  
Magnetic And Electric Properties ◽  
Wide Group

AbstractIron phosphates are a wide group of compounds that possess versatile applications. Their properties are strongly dependent on the role and position of iron in their structure. Iron, because of its chemical character, is able to easily change its redox state and accommodate different chemical surroundings. Thus, iron-phosphate crystallography is relatively complex. In addition, the compounds possess intriguing magnetic and electric properties. In this paper, we present crystal structure properties of a newly developed iron-phosphate compound that was obtained by devitrification from iron-phosphate glass of pyrophosphate stoichiometry. Based on X-ray diffraction (XRD) studies, the new compound (Fe7P11O38) was shown to adopt the hexagonal space group P63 (No. 173) in which iron is present as Fe3+ in two inequivalent octahedral and one tetrahedral positions. The results were confirmed by Raman and Mössbauer spectroscopies, and appropriate band positions, as well as hyperfine interaction parameters, are assigned and discussed. The magnetic and electric properties of the compound were predicted by ab initio simulations. It was observed that iron magnetic moments are coupled antiferromagnetically and that the total magnetic moment of the unit cell has an integer value of 2 µB. Electronic band structure calculations showed that the material has half-metallic properties.

Calculated electronic band structure and magnetic moments of ferrites

1992 ◽  
Vol 103 (1-2) ◽  
pp. 212-220 ◽  
Author(s):  
M. Pénicaud ◽  
B. Siberchicot ◽  
C.B. Sommers ◽  
J. Kübler
Keyword(s):  
Band Structure ◽  
Electronic Band Structure ◽  
Magnetic Moments ◽  
Electronic Band

scholarly journals Antiferromagnetic Ordering and Transport Anomalies in Single-Crystalline CeAgAs2

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3865
Author(s):  
Maria Szlawska ◽  
Daniel Gnida ◽  
Piotr Ruszała ◽  
Maciej J. Winiarski ◽  
Małgorzata Samsel-Czekała ◽  
...  
Keyword(s):  
Electrical Transport ◽  
Electronic Band Structure ◽  
Chemical Vapor ◽  
Chemical Vapor Transport ◽  
Gap Formation ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Antiferromagnetic Ordering ◽  
Structure Calculations ◽  
Distinct Increase

Single crystals of the ternary cerium arsenide CeAgAs2 were grown by chemical vapor transport. They were studied by means of x-ray diffraction, magnetization, heat capacity and electrical transport measurements. The experimental research was supplemented with electronic band structure calculations. The compound was confirmed to order antiferromagnetically at the Néel temperature of 4.9 K and to undergo metamagnetic transition in a field of 0.5 T at 1.72 K. The electrical resistivity shows distinct increase at low temperatures, which origin is discussed in terms of pseudo-gap formation in the density of states at the Fermi level and quantum corrections to the resistivity in the presence of atom disorder due to crystal structure imperfections.

scholarly journals On the New Oxyarsenides Eu5Zn2As5O and Eu5Cd2As5O

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 475
Author(s):  
Gregory Darone ◽  
Sviatoslav Baranets ◽  
Svilen Bobev
Keyword(s):  
Electronic Band Structure ◽  
Charge Balance ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Cell Parameters ◽  
Pearson Symbol ◽  
Formal Charge ◽  
Valence Electrons ◽  
Metal Flux ◽  
Structure Calculations

The new quaternary phases Eu5Zn2As5O and Eu5Cd2As5O have been synthesized by metal flux reactions and their structures have been established through single-crystal X-ray diffraction. Both compounds crystallize in the centrosymmetric space group Cmcm (No. 63, Z = 4; Pearson symbol oC52), with unit cell parameters a = 4.3457(11) Å, b = 20.897(5) Å, c = 13.571(3) Å; and a = 4.4597(9) Å, b = 21.112(4) Å, c = 13.848(3) Å, for Eu5Zn2As5O and Eu5Cd2As5O, respectively. The crystal structures include one-dimensional double-strands of corner-shared MAs4 tetrahedra (M = Zn, Cd) and As–As bonds that connect the tetrahedra to form pentagonal channels. Four of the five Eu atoms fill the space between the pentagonal channels and one Eu atom is contained within the channels. An isolated oxide anion O2– is located in a tetrahedral hole formed by four Eu cations. Applying the valence rules and the Zintl concept to rationalize the chemical bonding in Eu5M2As5O (M = Zn, Cd) reveals that the valence electrons can be counted as follows: 5 × [Eu2+] + 2 × [M2+] + 3 × [As3–] + 2 × [As2–] + O2–, which suggests an electron-deficient configuration. The presumed h+ hole is confirmed by electronic band structure calculations, where a fully optimized bonding will be attained if an additional valence electron is added to move the Fermi level up to a narrow band gap (Eu5Zn2As5O) or pseudo-gap (Eu5Cd2As5O). In order to achieve such a formal charge balance, and hence, narrow-gap semiconducting behavior in Eu5M2As5O (M = Zn, Cd), europium is theorized to be in a mixed-valent Eu2+/ Eu3+ state.

Transmissionsoptimierte Einkristallstrukturbestimmung und elektronische Struktur von Bi3Ni / Transmission-Optimized Single-Crystal Structure Determination and Electronic Structure of Bi3Ni

2006 ◽  
Vol 61 (7) ◽  
pp. 785-791 ◽  
Author(s):  
Michael Ruck ◽  
Tilo Söhnel
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Electronic Band Structure ◽  
Structural Fragment ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Interatomic Distances ◽  
X Ray ◽  
Absorption Correction ◽  
Trigonal Prismatic Coordination

Crystals of Bi3Ni were synthesized using iodine as mineralizer. X-ray diffraction on a single-crystal including transmission-optimized measurement and optimized absorption correction (μ(Mo-Kα) = 1302 cm−1) results in a structure model (Pnma; a = 887.96(7), b = 409.97(3), c = 1147.8(1) pm) with significant deviations in interatomic distances compared with previous data from X-ray and neutron investigations. From quantum chemical calculations and from the structural chemistry of the subhalides related to Bi3Ni the chemical structure of the intermetallic compound can be derived. In the crystal structure the Ni atoms have a capped trigonal prismatic coordination of Bi atoms with strong bonds Ni-Bi and Ni-Ni. The prisms constitute rods 1∞ [NiBi1/1Bi6/3] by sharing the non-capped square faces. The bonding between the intermetallic rods is clearly weaker than inside them, leading to a preservation of this structural fragment in the subhalides of Bi3Ni. In accordance with the low temperature superconductivity of the compound, its electronic band structure shows steep and flat bands at the Fermi level. DFT and ELF calculations reveal a separation of delocalized conduction electrons inside the prism rods and largely localized valence electrons between them.

scholarly journals Femtosecond electron-phonon lock-in by photoemission and x-ray free-electron laser

Science ◽  
2017 ◽  
Vol 357 (6346) ◽  
pp. 71-75 ◽  
Author(s):  
S. Gerber ◽  
S.-L. Yang ◽  
D. Zhu ◽  
H. Soifer ◽  
J. A. Sobota ◽  
...  
Keyword(s):  
Coupling Strength ◽  
Electronic Band Structure ◽  
Phonon Coupling ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
Structure Comparison ◽  
X Ray ◽  
Iron Selenide ◽  
Electron Phonon Coupling ◽  
Lock In

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a “coherent lock-in” measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

THE ELECTRONIC BAND STRUCTURES FOR AN ANTIFERROMAGNETIC STATE OF Cu2Sb-TYPE INTERMETALLIC COMPOUND Cr2As

1993 ◽  
Vol 07 (01n03) ◽  
pp. 770-773 ◽  
Author(s):  
M. SHIRAI ◽  
T. KAWAMOTO ◽  
K. MOTIZUKI
Keyword(s):  
Intermetallic Compound ◽  
Electronic Band Structure ◽  
Magnetic Moments ◽  
Partial Density ◽  
Energy Splitting ◽  
Antiferromagnetic State ◽  
Good Correspondence ◽  
Electronic Band ◽  
Linearized Augmented Plane Wave ◽  
Electronic Band Structures

Electronic band structure calculations are carried out for the antiferromagnetic state of an intermetallic compound Cr2As, having the Cu2Sb-type crystal structure, by using a self-consistent linearized augmented-plane-wave (LAPW) method. The partial density of states (DOS) for Cr (II) 3d states shows a small energy splitting (about 1 eV) between the spin-up and spin-down bands, while that for Cr (I) 3d states hardly shows. The magnetic moments at Cr (I) and Cr (II) sites are evaluated to be 0.33μB and 1.37µB per atom, respectively. These values agree well with the observed values. The calculated DOS shows good correspondence with photoemission and inverse photoemission spectra measured recently.

Single-Crystal X-Ray Diffraction and Electronic Band Structure Studies of PdTeI

1998 ◽  
Vol 137 (2) ◽  
pp. 206-210 ◽  
Author(s):  
D.-K. Seo ◽  
M.-H. Whangbo ◽  
K. Neininger ◽  
G. Thiele
Keyword(s):  
Band Structure ◽  
Single Crystal ◽  
Electronic Band Structure ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
X Ray

scholarly journals Synthesis, structural characterization, and electronic structure of the novel Zintl phase Ba2ZnP2

2020 ◽  
Vol 76 (9) ◽  
pp. 869-873
Author(s):  
Adam Balvanz ◽  
Sviatoslav Baranets ◽  
Svilen Bobev
Keyword(s):  
Electronic Band Structure ◽  
Structure Type ◽  
The Novel ◽  
X Ray Diffraction ◽  
Orthorhombic Space Group ◽  
Zintl Phase ◽  
Electronic Band ◽  
Intrinsic Semiconductor ◽  
Valence Electrons ◽  
First Time

The novel Zintl phase dibarium zinc diphosphide (Ba2ZnP2) was synthesized for the first time. This was accomplished using the Pb flux technique, which allowed for the growth of crystals of adequate size for structural determination via single-crystal X-ray diffraction methods. The Ba2ZnP2 compound was determined to crystallize in a body-centered orthorhombic space group, Ibam (No. 72). Formally, this crystallographic arrangement belongs to the K2SiP2 structure type. Therefore, the structure can be best described as infinite [ZnP2]4− polyanionic chains with divalent Ba2+ cations located between the chains. All valence electrons are partitioned, which conforms to the Zintl–Klemm concept and suggests that Ba2ZnP2 is a valence-precise composition. The electronic band structure of this new compound, computed with the aid of the TB–LMTO–ASA code, shows that Ba2ZnP2 is an intrinsic semiconductor with a band gap of ca 0.6 eV.

The Structural, Electronic, Optical and Thermo-Electric Properties of Oxynitride Perovskite CaTaO2N

SPIN ◽  
2020 ◽  
Vol 10 (01) ◽  
pp. 2050007
Author(s):  
K. Hocine ◽  
O. Cheref ◽  
K. Bettine ◽  
D. Rached ◽  
S. Benalia ◽  
...  
Keyword(s):  
Band Structure ◽  
Figure Of Merit ◽  
Density Functional ◽  
Electronic Band Structure ◽  
Structural Parameters ◽  
Electric Properties ◽  
Partial Density ◽  
Full Potential ◽  
Thermo Electric ◽  
Electronic Band

In this study, we carried out ab-initio calculations of structural, electronic, optical and thermo-electric properties of CaTaO2N compound in Pnma orthorhombic structure, using the full-potential linearized augmented plane wave method (FP-LAPW), within the framework of density functional theory (DFT). The calculated structural parameters are found to be in good agreement with the experimental results. Moreover, we have studied the electronic band structure, total and partial density of states in order to explain the origin of band gaps and the nitrogen anion contribution in the valence and the conduction bands. The CaTaO2N band structure has shown a direct band gap in the direction [Formula: see text] (with the value 2.32[Formula: see text]eV). The optical properties represented by the dielectric functions for CaTaO2N compound have revealed that the Pnma structure absorbs the light at a large window in the edge UV-Vis regions. In order to explain the thermo-electric properties, we have calculated Seebeck coefficient, electrical conductivity, thermal conductivity and the factor figure of merit in this temperature range 100–1000 K. The factor figure of mérit (ZT) of CaTaO2N takes a maximum value of 0.775 at [Formula: see text][Formula: see text]K.

scholarly journals Structural Features of Y2O2SO4 via DFT Calculations of Electronic and Vibrational Properties

Materials ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3246
Author(s):  
Aleksandr S. Oreshonkov ◽  
Yuriy G. Denisenko
Keyword(s):  
Density Functional ◽  
Dielectric Material ◽  
Electronic Band Structure ◽  
Density Functional Theory Calculations ◽  
Structural Features ◽  
Spectral Lines ◽  
Partial Density ◽  
X Ray Diffraction ◽  
Electronic Band ◽  
The Difference

The traditional way for determination of molecular groups structure in crystals is the X-Ray diffraction analysis and it is based on an estimation of the interatomic distances. Here, we report the analysis of structural units in Y2O2SO4 using density functional theory calculations of electronic properties, lattice dynamics and experimental vibrational spectroscopy. The Y2O2SO4 powder was successfully synthesized by decomposition of Y2(SO4)3 at high temperature. According to the electronic band structure calculations, yttrium oxysulfate is a dielectric material. The difference between the oxygen–sulfur and oxygen–yttrium bond nature in Y2O2OS4 was shown based on partial density of states calculations. Vibrational modes of sulfur ions and [Y2O22+] chains were obtained theoretically and corresponding spectral lines observed in experimental Infrared and Raman spectra.

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